Enhanced hydroxyl radical generation in the combined ozonation and electrolysis process using carbon nanotubes containing gas diffusion cathode

Abstract

Combination of ozone together with electrolysis (ozone-electrolysis) is a promising wastewater treatment technology. This work investigated the potential use of carbon nanotube (CNT)-based gas diffusion cathode (GDC) for ozone-electrolysis process employing hydroxyl radicals (·OH) production as an indicator. Compared with conventional active carbon (AC)-polytetrafluoroethylene (PTFE) and carbon black (CB)-PTFE cathodes, the production of ·OH in the coupled process was improved using CNTs-PTFE GDC. Appropriate addition of acetylene black (AB) and pore-forming agent Na2SO4 could enhance the efficiency of CNTs-PTFE GDC. The optimum GDC composition was obtained by response surface methodology (RSM) analysis and was determined as CNTs 31.2 wt%, PTFE 60.6 wt%, AB 3.5 wt%, and Na2SO4 4.7 wt%. Moreover, the optimized CNT-based GDC exhibited much more effective than traditional Ti and graphite cathodes in Acid Orange 7 (AO7) mineralization and possessed the desirable stability without performance decay after ten times reaction. The comparison tests revealed that peroxone reaction was the main pathway of ·OH production in the present system, and cathodic reduction of ozone could significantly promote ·OH generation. These results suggested that application of CNT-based GDC offers considerable advantages in ozone-electrolysis of organic wastewater.

Facile Photoinduced Generation of Hydroxyl Radical on a Nitrocellulose Membrane Surface and its Application in the Degradation of Organic Pollutants

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As imple, clean, and efficient method has been developed for generating hydroxyl radicals on an itrocellulose membrane (NCM) under light of wavelengths greater than 280 nm. [5] Av ariety of methods have been developed for the productiono fh ydroxyl radicals,s uch as the Fenton reaction, [6] ozonation, [7] ultrasonication, [8] ultraviolet irradiation, [9] high-energyr adiation, [10] plasmon excitation, [11] electrochemical process, [12] and TiO 2 photocatalysis. Radical generation was shown to be dependent on the nature of the NCM and light, and independent of the properties of the bulk solution.The quantum yield for hydroxyl radicals from the NCM was 1.72 10 À4 ,w hich is approximately 2.46 times that from TiO 2 .T his hydroxyl radical generation method was preliminarilya pplied in the photodegradation of organic pollutants, in whiche lectrostatic interactions between the pollutant molecules and the NCM surface were found to play ak ey role.

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“…Because of its high oxidizing potential, the hydroxyl radical nonselectively reacts with numerous organic substances at near diffusion-controlled rates, [1] thus playing au nique role in biochemical processes, [2] inorganic and organic synthesis, [3] DNA structurei dentification, [4] and wastewater treatment. [5] Av ariety of methods have been developed for the productiono fh ydroxyl radicals,s uch as the Fenton reaction, [6] ozonation, [7] ultrasonication, [8] ultraviolet irradiation, [9] high-energyr adiation, [10] plasmon excitation, [11] electrochemical process, [12] and TiO 2 photocatalysis. [13] However,t hese methods have severali nherent drawbacks, such as high cost, interfer-ence from concomitantr eactive species, the requirement of precursors, secondary pollution from catalysts or precursors, and difficulties in catalyst recovery, all of which complicate the widespreada pplication of these methods.…”

Degradation of Octocrylene Using Combined Ozonation and Electrolysis Process: Optimization by Response Surface Methodology

“…and ) and catholic reduction of O 3 (Eqs. and ) . …”

“…The reactor with a width of 100 mm, depth of 50 mm, and height of 150 mm, with a working volume of 500 mL. According to previous reports , a 7 cm 2 carbon nanotubes‐based gas diffusion electrode was prepared and employed as the cathode, and a 0.8 cm 2 Pt wire was used as the anode. The electrode gap was 15 mm.…”

Electrochemical Aging and Halogen Oxides Formation on Multiwalled Carbon Nanotubes and Fe3O4@g-C3N4 Coated Conductive Membranes

“…60 The halogenated byproduct formation on the two presented composite conductive membranes has not been reported elsewhere. Figure 5 62 After the electrochemical aging process, the concentrations of all halogenated anions decreased due to the loss of catalyst activity or reactive sites. After membrane aging, oxygen-containing functional groups were introduced that are capable of interfering with electron transport in the sp2 carbonaceous structure.…”